We know Peter was limited and Thompson was good but was 37 the first time Wlad fought him, even older than Rahman was and he was never a dangerous puncher.
And by cruiserweights fighting the Wlad I mean Chris Byrd, Jean Marc Mormeck and Eddie Chambers. Sure Byrd and Chambers scored their best wins at heavy, but they were the lightest punchers in the division.
I don't blame the Klitschkos for fighting cruiserweights, old fighters and green up-and-comers. The division is so thin and limited and the champs have to fight somebody.

Haye is an overachiever 4sure but as an heavyweight he really was not a great puncher. Lewis, Bowe and even Holyfield carried much more power and I rate their skills far beyond all of of the guys the Klitschko's have faced.

I don't think they would hold titles. Even if both brothers were there and the punchers were sent to Vitali to fight. There were a better crop of heavyweights. Can't messure how good they would do by how they did against the bunch they got to fight in this era.